In recent years, various recording media for digital data such as DVD (Digital Versatile Disc), etc., have been popularized, and optical disc recording/reproducing apparatuses of large capacity adapted for performing write-once operation or rewrite operation of data to optical discs such as DVD-R (Recordable), or DVD-RW (ReWritable), etc., which are recordable recording media, have been put into practical use. In the apparatuses of this kind, data write operation is performed with address information of block included at pits, wobbled grooves or lands, etc., which are formed in advance on the disc essentially on the error correction (ECC) block basis.
In this instance, it is necessary to consider the system of linking between block and block. With respect to the linking, two systems have been proposed until now when roughly classified.
One system is a system in which importance to compatibility with read only optical disc is attached so that blocks are written in such a manner that they are successive without break in the state where there is no linking portion. As examples employing this system, DVD-R, DVD-RW and/or DVD+RW are mentioned.
The other system is a system in which compatibility with the reproduction only unit of the reproduction only optical disc is disregarded so that linking portions, pit portions used for address information prepared in advance, etc., and/or gap portions of those portions exist between block and block. For example, DVD-RAM employs this system.
In the conventional system, there are problems as described below, for example, in regard to compatibility and/or random accessibility.
First, in the system of writing block without break in the state where there is no linking portion between blocks, write position accuracy of high accuracy is required as compared to the system where there is linking area in write operation of block by random access. As a result, the circuit therefor becomes more complicated, and this is disadvantage in point of cost. Moreover, in readout operation, there are instances where phases of channel bits of block to be read out and block precedent thereto becomes discontinuous. For this reason, if such a measure for giving limitation to the phase relationship of channel bits between blocks such as a method of continuously writing block to be read out and block precedent thereto, etc. is not employed, channel bit phase discontinuous portion between blocks results in disturbance with respect to PLL (Phase Locked Loop) of read-out clock. As a result, there is the possibility that read-out of data may not be stable for a time period until the time when PLL is placed in steady state so that read-out data error takes place. However, when limitation is given to the phase relationship of channel bits between blocks, random accessibility and/or preservation efficiency of data onto the disc may be damaged, e.g., block precedent to write block also must be written as dummy block, etc.
Further, in the system in which gap portion exists between blocks, in the case where the reproduction only unit of the reproduction only optical disc is used to attempt to reproduce recordable optical disc, difference between physical specifications between the recordable optical disc and the reproduction only optical disc must be taken into consideration. For example, it is necessary to design reproduction system circuit such as Auto Gain Control (AGC), etc., in consideration of the fact that the portion where there is no amplitude, i.e., gap exists in reproduction waveform. For this reason, it is required to switch operation mode of the circuit between reproduction of the reproduction only optical disc and reproduction of reproducible/recordable optical disc, or to switch the circuit itself, leading to elevation of the apparatus cost.
As stated above, in the conventional linking form, when importance to cost is attached, it is the actual circumstances that there is nothing but way to select any one of hardware compatibility with the reproduction only optical disc and random accessibility.